With increasing use of high-frequency application, parasitic effects with parasitic resistance and capacitance generated by high-frequency operation have become more significant in the field of semiconductor process. For example, a complementary metal-oxide-semiconductor (CMOS) device of single well is formed on a signal well that is disposed on a substrate, and the CMOS device of single well may be interfered by a parasitic effect between the well and the substrate when operating at a high-frequency. In order to deal with the problem, a solution of multi-well may be used to form a semiconductor element. For example, a transistor of triple-well has been used. An improved isolation effect is provided by using multiple wells. However, for applications of higher frequencies such as radio frequency (RF) applications, unwanted parasitic effects are more significant and yet difficult to avoid. Hence, a solution is required to reduce parasitic effects of semiconductor elements in the field.